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Collybia sp.?
Collybia are characterized by white spores, incurved cap margin, central cartilaginous stipe, and fruit bodies which decay easily ("putrescent").
Tropical area of Mexico.
Could be a Collybia species, but I cannot tell without a underside view. Definitely not a Russula, Lars. Because it has a collyboid/mycenoid habitus: slim and long stem, thin cap. Russulas have a more firm posture, cilindrical stem, thicker cap, lower stemlength to capwidth ratio (which means that the stemlength is often as long as the cap is in diameter).